Dhriti Ranjan Saha

Magnetodielectric Effect in Graphene-PVA Nanocomposites

Graphene-polyvinyl alcohol (PVA) nanocomposite films with thickness of 120 μm were synthesized by solidification of PVA in a solution with dispersed graphene nanosheets. Electrical conductivity data were explained as arising due to hopping of carriers between localized states formed at the graphene-PVA interface. Dielectric permittivity data as a function of frequency indicated the occurrence of Debye-type relaxation mechanism. The nanocomposites showed a magnetodielectric effect with the dielectric constant changing by 1.8% as the magnetic field was increased to 1 T. The effect was explained as arising because of Maxwell–Wagner polarization as applied to an inhomogeneous 2D, two-component composite model. This type of nanocomposite may be suitable for applications involving nanogenerators.

Nanoindentation studies on silver nanoparticles

Nanodimensional metallic silver was grown by electrodeposion technique in a semi solid polymer matrix of polyacrylamide. The whole structure looks like dendronic. The average particle diameter of the as grown metallic silver is 13 nm. Nanoindentation study of these nanoparticles shows modulus and hardness value as 103.93 GPa and 3.12 GPa respectively.

Viscoelastic properties of graphene/PVA nanocomposite

Graphene/Polyvinyl alcohol (PVA) nanocomposite was synthesized with a graphene content of 1wt%. Viscoelastic properties were studied using a Dynamical Mechanical Analyzer. The composite showed a higher storage modulus as compared to PVA up to 275K. Thereafter there was a crossover to a lower value. The glass transition temperature for the composite was found to be smaller by 26K than that of pure PVA. This is believed to be occurring because of a reduction of surrounding entanglements of the polymer molecules due to the presence of graphene sheets.

Study of dielectric relaxation process in nanocomposite of Li2O−SiO2 nanoglass-CuO nanoparticles

Dielectric behaviour of a nanocomposite consisting of 23Li2O⋅77SiO2 nanoglass within the pores of compacted CuO nanoparticles was studied. Real and imaginary parts of dielectric permittivity of the material were measured over the temperature range 313 to 363 K. The results indicated a relaxation behaviour. The data were explained by a space charge polarization model developed in the case of a laminar conductor. The activation energy of the relaxation process was in close agreement with that of lithium ion conduction in the nanoglass.

Nanoindentation measurements on nanostructured silver grown within a gel derived silica glass by electrodeposition

Mechanical Properties of silver nanoparticles were investigated. Sliver nanophase with particle diameters in the range 11.1 to 36 nm was grown in silica based gel derived glasses by an electrodeposition technique. Nanoindentation measurements were carried out on the silver particles. Hardness as well as modulus values decreased with a lowering of the silver particle diameter. This inverse Hall Petch Effect was analysed on the basis of Conrad-Narayan model of grain boundary sliding which involved silver diffusion along the grain surface. The activation energy extracted was in excellent agreement with the activation energy of grain boundary diffusion in bulk silver as reported earlier.

Nanoindentation studies on composites of CuO nanoparticles-lithia silica nanoglass

Nanoindentation of CuO-lithia silica nanoglass (CuO-NG) composite was studied and compared with only CuO nanoparticles (CuO). Youngs Modulus (E) and hardness (H) of the composite was found to be greater in comparison with CuO nanoparticles. Creep measurements showed that Creep strain rate (CSR) is lower for composite material than only CuO. This is due to decrease of copper diffusion through nanoglass phase in composite sample.